refactor(apps): move forte-drop postgres from infra to apps

Per reviewer (danijel): forte-drop's DB deployment belongs in apps/,
not infra/. Straight relocation — same structure (Application +
resources/ subdir), source.path updated to apps/base/forte-drop-postgresql/resources,
wired into apps/overlays/upc-dev. Backup CronJob + RESTORE.md + sealed
pg creds move with it.

Consolidates the whole forte-drop deployment (postgres + web + mcp)
under apps/. The infra PR (#17) is now superseded by this.

apps/base/forte-drop-postgresql/resources/postgresql.yaml

@@ -0,0 +1,105 @@
+apiVersion: v1
+kind: Service
+metadata:
+  name: forte-drop-postgresql
+  namespace: forte-drop
+  labels:
+    app.kubernetes.io/name: postgresql
+    app.kubernetes.io/instance: forte-drop
+    app.kubernetes.io/component: database
+spec:
+  type: ClusterIP
+  ports:
+  - name: tcp-postgresql
+    port: 5432
+    targetPort: tcp-postgresql
+  selector:
+    app.kubernetes.io/name: postgresql
+    app.kubernetes.io/instance: forte-drop
+---
+apiVersion: apps/v1
+kind: StatefulSet
+metadata:
+  name: forte-drop-postgresql
+  namespace: forte-drop
+  labels:
+    app.kubernetes.io/name: postgresql
+    app.kubernetes.io/instance: forte-drop
+    app.kubernetes.io/component: database
+spec:
+  serviceName: forte-drop-postgresql
+  replicas: 1
+  selector:
+    matchLabels:
+      app.kubernetes.io/name: postgresql
+      app.kubernetes.io/instance: forte-drop
+  template:
+    metadata:
+      labels:
+        app.kubernetes.io/name: postgresql
+        app.kubernetes.io/instance: forte-drop
+        app.kubernetes.io/component: database
+    spec:
+      containers:
+      - name: postgresql
+        image: postgres:16-alpine
+        # NOTE: no securityContext. The official postgres image's entrypoint must
+        # start as root to chown a fresh /var/lib/postgresql/data, then drops to
+        # the postgres user (uid 70 in alpine) via gosu. Forcing runAsNonRoot here
+        # breaks initdb on a fresh PVC. Matches the vaultwarden-postgresql pattern.
+        ports:
+        - name: tcp-postgresql
+          containerPort: 5432
+        env:
+        - name: POSTGRES_USER
+          valueFrom:
+            secretKeyRef:
+              name: forte-drop-pg-creds
+              key: pgusername
+        - name: POSTGRES_PASSWORD
+          valueFrom:
+            secretKeyRef:
+              name: forte-drop-pg-creds
+              key: pgpassword
+        - name: POSTGRES_DB
+          value: drops
+        - name: PGDATA
+          value: /var/lib/postgresql/data/pgdata
+        volumeMounts:
+        - name: data
+          mountPath: /var/lib/postgresql/data
+        livenessProbe:
+          exec:
+            command:
+            - sh
+            - -c
+            - pg_isready -U "$POSTGRES_USER" -d drops
+          initialDelaySeconds: 30
+          periodSeconds: 10
+        readinessProbe:
+          exec:
+            command:
+            - sh
+            - -c
+            - pg_isready -U "$POSTGRES_USER" -d drops
+          initialDelaySeconds: 5
+          periodSeconds: 5
+        resources:
+          requests:
+            cpu: 100m
+            memory: 256Mi
+          limits:
+            cpu: 500m
+            memory: 512Mi
+  volumeClaimTemplates:
+  - metadata:
+      name: data
+      annotations:
+        argocd.argoproj.io/sync-options: Prune=false,Delete=false
+    spec:
+      accessModes:
+      - ReadWriteOnce
+      storageClassName: upcloud-block-storage-maxiops
+      resources:
+        requests:
+          storage: 5Gi